The invention relates to a gas conducting system, which can be used particularly as a pressurized air system for motor vehicles and is provided with a filter for moisture removal. The invention further relates to a filter containing a desiccant.
Filters containing desiccants are known. DE 196 50 185 discloses a replaceable cartridge in the form of an air dryer fixed in the mounting location by a screw-on cover, which makes it possible for the gas that has to be dried to flow through. These filters, which are referred to as a desiccant boxes, are used for instance in air brake systems of trucks and buses for removing moisture the compressor air to prevent corrosion and icing up of the brake system.
At very low temperatures and under unfavorable operating conditions, however, the control valve for the compressor in the brake system may freeze. Consequently, an unacceptably high pressure builds up and may cause the brake system to fail. In this case, the housing of the desiccant box is at risk since it is usually the weakest part in the gas conducting system. An explosion of the housing presents an enormous safety risk, which affects not only the function of the motor vehicle but may jeopardize the health of the passengers.
It is therefore the object of the invention to provide a filter for removing moisture for air in an air conducting system.
Another object of the invention is to provide a moisture removing filter which is not subject to bursting if subjected to excessive internal air pressures.
A further object of the invention is to provide a moisture removing filter which is protected against bursting under excessive pressure and yet can be manufactured at reasonable cost.
These and other objects are achieved in accordance with the present invention by providing a gas conducting system which includes a filter for removing moisture from a gas passed therethrough, in which the filter is provided with a desiccant arranged in a filter housing structure having an inlet and an outlet for the gas to flow through, and in which the housing structure is provided with a seal which seals the housing relative to the surrounding environment of the gas conducting system, and the seal comprises at least one weakened area with a lower pressure limit for failure than the rest of the seal.
In accordance with a further aspect of the invention, the objects are achieved by providing a moisture removing filter comprising a desiccant arranged in a housing structure, the filter having a seal for sealing the housing structure relative to the surrounding environment of the housing structure, in which the seal comprises at least one weakened area with a lower pressure limit for failure than the rest of the seal.
The gas conducting system according to the invention comprises a filter with a housing structure, which is made tight against the environment of the gas conducting system by means of a seal. The seal is thus provided between the housing structures containing the duct system for the gas from which moisture is to be removed and the environment. The housing structure can be a separate housing for the filter or form an integral component of the gas conducting system. In the latter case, it is possible, for instance, to design the housing structure in such a way that it can be opened to replace the desiccant.
The invention is characterized in that the seal has at least one weakened area designed to fail at a lower limit pressure than the remainder of the seal. This weakened area is designed as a predetermined weak point for targeted failure of the seal. Failure of the seal occurs in a pressure range that lies outside the normal operating range of the gas conducting system but is below the critical pressures for the housing structure of the filter. This effectively counteracts an explosive failure of the housing structure and thereby enhances the safety of the component.
In accordance with a further embodiment of the invention, the filter may be designed as a disposable filter. In this case, the desiccant in the filter cannot be replaced. To renew the desiccant, the entire disposable filter must be replaced. The described configuration as a disposable filter makes it possible to create particularly cost-effective and safe filter systems.
In another variant of the invention, the housing structure of the filter can be opened and the desiccant replaced. The possibility of replacing the desiccant in this embodiment minimizes waste. The housing can be reused so that only the insert with the desiccant has to be disposed of in some manner. This is a solution that is environmentally sound and also economical over prolonged operation.
In accordance with one specific embodiment of the invention, the weakened area of the seal, which is designed as a predetermined weak point, is formed by a cross section that is reduced compared to the rest of the seal. The geometry of the cross-sectional reduction is selected in such away that under normal operating pressures a seal is produced even at the point of the weakened area. Only an excessive increase in the operating pressure causes the weakened area to fail. The permissible operating pressure can be exceeded multiple times if the seal is designed accordingly. As soon as the operating pressure drops again to the permissible range, the sealing function of the seal is completely restored.
As an alternative to a cross-sectional reduction, a different sealing material can be selected to produce the weakened area. In this case, the sealing ring can be produced by a two-component molding technique.
In accordance with another specific embodiment of the invention, the seal with the weakened area is provided between the housing structure containing the desiccant and the mounting location on the gas conducting system. This is a housing structure that can be removed from the gas conducting system. The seal required at this location can advantageously be equipped with the described predetermined weak point without causing any additional design complexity. At the same time, this creates a good opportunity at the mounting location to replace the seal and thereby to prevent loss of function due to aging.
Advantageously, the seal can be fixed in a recess in the mounting location. When the housing structure is removed, the seal thus remains, for instance, in a groove in the mounting location. The seal can of course also be fixed to a device on the housing structure that is specially provided for this purpose so that it remains on the housing structure when the housing structure is disassembled.
Another option is to arrange the seal between two different housing parts of the housing structure. If these housing parts are designed so that they can be opened for desiccant replacement, the weakened area can be accommodated in the seal between the housing parts, which seal is required in any case. This does not create any additional design complexity.
One particular embodiment of the invention provides that the weakened area be made of a material having essentially constant sealing properties within a temperature range specified for the gas conducting system. Venting through the weakened area of the seal can then be achieved independently of the momentary operating temperature. This makes it possible, for instance, to eliminate a pressure control valve in the gas conducting system, which increases the economic efficiency of the entire system.
In a case like that described above in which the seal has to be used only if the pressure control valve ices up, the requirements for constant sealing properties are lower. The limit pressure at which the seal will start to leak has to be ensured only for the temperature range where there is a risk of icing, provided that this pressure increases with increasing temperatures. At higher temperatures, the functioning of the pressure control valve is assured, so that there is no need for the weakened area of the seal to be opened.
The invention furthermore comprises a filter with a housing structure, which has a seal with the previously described properties to seal the housing structure relative to its surrounding environment. This filter can be used, in particular, in a gas conducting system of the described type, such as an air brake system.
These and other features of preferred embodiments of the invention, in addition to being set forth in the claims, are also disclosed in the specification and/or in the drawings, and the individual features each may be implemented in embodiments of the invention either individually or in the form of subcombinations of two or more features and can be applied to other fields of use and may constitute advantageous, separately protectable constructions for which protection is also claimed.